Superfuel



Oct. 25, 1949. R. F. MARSCHNER 2,485,897

SUPER-FUEL Filed July 11, 1947 2 Sheets-Sheet 1 Volume Percenf Tripfane I00 80 60 40 20 0 Curve A Wif/ww n-hgpfane (C'a/cu/afed) 'urve Curve A Per cem [M8 (on C/ear lsoocfune) Blends di/ufea MM 20% n-hepfvne Acfua/ 0 20 40 50, I 80 I00 Volume Percenf Cyc/opgnfane IN V EN TOR.

I76 ENG/NE RAT/N65 0F Roberf I? Marsc/mer QCLOPENTANE-TR/PTANE BLENDS 81' (Fuel f0 Air Raf/'0 Shon g) M $741..

4fforney Patented Oct. 25, 1949 SUPERFUEL Robert F. Marschner, Homewood, 111., assignor to Standard Oil Company, Chicago, 111., a. corporation of Indiana Application July 11, 1947, Serial No. 760,460

4 Claims. (o1. 44 .s9)

This invention relates to a super fuel for high compression, internal combustion, spark ignition engines and the invention pertains more particularly to a fuel which will give maximum power output, particularly in aviation engines.

Isooctane has been employed as a standard for rating the potential power output of a motor fuel and isooctane has been blended with many other hydrocarbons in the manufacture of aviation gasolines. Thus in my United States Patent 2,407,716 I have shown the remarkable properties of blends of isooctane with cyclopentane and dimethyl butanes. Triptane has been considered the ultimate as a super fuel for high compression engines as pointed out, for example, in The effect of the molecular structure of fuels on the power and efficiency of internal combustion engines by Charles F. Kettering (Industrial and Engineering Chemistry, volume 36 (1944) pages 1079-1085). Many blends or mixtures of hydrocarbons have been proposed'for high compression aviation engines but heretofore none of them has been superior in power output to triptane or a cyclopentane-dimethyl butane mixture. The object of this inventoin is to provide a motor fuel with a greater power output than any motor fuel heretofore known.

Power output is conventionally measured by the indicated mean effective pressure" (or IMEP) in pounds per square inch because for any particular engine running at constant speed the horsepower varies directly with the IMEP. The absolute values of IMEP depend of course on the particular engine and conditions employed for testing and usually a fuel is rated on the comparative basis with isooctane. An object of my invention is to provide a motor fuel which will have maximum power output or IMEP under conditions approximating those employed for making specification tests with fuel: air ratios of the order of about .08 to .14, maximum power output being in the range of about .12 to .13 (i. e. 0.12:1 to 0.13:1).

I have discovered that a mixture of about 25% to 75% by volume of triptane and about 75% to 25% by volume of cyclopentane, particularly when the triptane: cyclopentane ratio is approximately 6:4, provides a motor fuel whose IMEP is substantially greater than that of either component of the mixture or any other known clear motor fuel or motor fuel blend. By adding l ad tetraethyl to the triptane-cyclopentane blend in amounts of 2 to 6 orpreferably about 4 :c. of lead tetraethyl fluid per gallon of said fuel alend, the IMEP can be still further increased 2 so that it can exceed that of any leaded fuel heretofore known to the art.

It has been shown that when triptane is admixed or blended with isooctane the IMEP of the various blends falls along a substantially-straight line--i. e., the effects of these two components are simply additive and the larger the amount of triptane in the blend the larger will be the IMEP of the blended fuel. Similar effects have been shown for blends of isooctane and dimethyl butanes. However, a 6:4 triptane-cyclopentane blend has an IMEP or potential power output which is substantially greater than that of either component of the blend so that increasing the triptane content of the blend beyond such optimum actually decreases the IMEP of the blended fuel. For maximum power output the blend should thus have at least 25% and preferably about 40% of each component.

The invention will be more clearly understood from the following detailed description and from the accompanying drawings which form a part of the specification and in which Figure 1 is a graph showing engine ratings of cyclopentane-triptane blends as compared with isooctane at fuelzair ratios of .09 and .10, and

Figure 2 is a graph showing engine ratings of cyclopentane-triptane blends in absolute values of pounds the effect of higher fuekair ratios and added lead tetraethyl to the blends.

My invention will be illustrated by comparative tests made in an engine simulating the standard 3-C test engine on fuel blends containing 100% triptane, triptane:20% cyclopentane, 60% triptane:40% cyclopentane, 40% triptane:60% cyclopentane, and cyclopentane. In the actual test procedure the above blends were cut back or diluted with exactly 20.0% added normal heptane in order that comparative tests could be made in the available test engine. Such diluent wasemployed because both cyclopentane and triptane are extremely sensitive and because the blending effects are smaller at severe engine conditions (high temperature). Since the abnormal behavior of cyclopentane is difficult to distinguish in unsupercharged tests, it was considered impractical to establish the presence of synergism with the straight fuels. It did not seem probable that the presence of lead would alter the nature of the blending curve and it was believed to be more reliable as well as easier to run these tests on unleaded blends. From the mass of data and correlations known to the art in this field the IMEP of straight triptane-cycloper square inch and also indicating between about .085

- out by the data is 40% with a range of 25-75% triptane lected to simulate rich mixture specification testcondiiions; the engine was run at 1800B. P. M. with a jacket temperature of 300 R, an air inlet temperature of 225 F. and the spark advanced 26 degrees. Such conditions might'be described as being intermediate in severity. .That. section of the IMEP vs. fuel to 'air (F./A.) curve and .102 was determined. Values of fuelzair ratios of .09 and .10 were obtained by plotting and interpolation. The data obtained in these tests are as follows:

Ratings of clear cyclopentane-triptane blends [All blends tested in presence of 20% normal heptane diluent.]

Vol. percent cyclopentane 40 60 Vol. percent triptane 100 80 60 40 IMEP of diluted blends at 0.09 F/A 130 139 131 13:; at 0.10 F/A 128 141 156 147 143 IMEP of diluted blends relative to clear iscoctane at 0.09 F/A 73 78 83 79 80 at 0.10 F/A 76 83 92 87 85 Calculated IMEP of undiluted blends relative to clear isooctane at 0.09 Fl 129 150 132 136 at 0.10 F/A 4 153 178 169 159 Blending IMEP oi undiluted blends at .09 F 190 216 250 222 229 at .10 F/A 210 258 320 286 267 at .12 FIA (extrapolated) (230) (300) (390) (350) (300) Calculated blending IMEP of undilutedhblefidsdwith 4 of lead tetraet ui er a on at .09 f lhnu iu f 270 300 350 310 320 at .10 F/A 290 360 450 400 370 at .12 WA (extrapolated).. (320) (420) (550) (490) (420) Assuming 50 IMEP for n-heptone under these conditions, and employing reciprocal IMEP formula.

The above data are plotted in Figure 1, the lower curves representing actual data and the upper curves representing the calculated comparison of the tested blends (in the absence of normal heptane) with clear isooctane. Curves A and A represent data obtained with fuel to air mixtures of about resent fuel to air mixtures of about .10. It is surprising that 100% triptane should have a lower IMEP rating than 100% cyclopentane; this anomaly may be due to the particular test conditions in the presence of the normal heptane diluent. The most surprising fact brought that there is an optimum blend of cyclopentane with triptane which has a substantially higher IMEP or potential power output than that of either component of the blend. For optimum IMEP both components should be present in amounts of at least about with 75-25% cyclopentane showing a power output which is superior to that of either component of the blend.

In Figure 2 similar data are plotted with the IMEP indicated in pounds per square inch and with additional points indicating the IMEP obtainable. Thus curve C and. curve D corresnond to curves A and B of Figure 1. Curve .09. Curves B and B rep- E illustrates the efiect of raising the fuelzair ratio to .12 using unleaded blends. Curve F illustrates the effect ofadding 4 cc. of lead tetraetliyl fluidper gallon. of, the various blends where the fuel to air ratio is-about' .10. It, will thus be seen that the' triptane-cyclopentane blends herein described are remarkabl-ysuperior in po'-- tential power output to any motor fuel heretofore known to the art. I

As hereinabove pointed out, each component of the triptane-cyclopentane blends should be present in an amount of atleast 25% and preferably at least about 40%. The addition of tetraethyl lead in amounts of.2 to 6 cc. per gallon markedly improves the potential power output.- For maximum power output the fuelzair ratio should be in the range of about .12 to .13. For

maximum power output the leaded blend should be substantially free from other hydrocarbons or di-luents. However, the blends herein described may be employed with other aviation base stocks particularly when the base stocks are employed in amounts less than 50% of the total fuel. The small amounts of dimethyl butanes which are frequently obtained along with cyclopentane are not particularly deleterious.

It should be noted that the super fuel hereinabove described contains no aromatics and olefins and hence has maximum heating or fuel value and maximum stability against gum formation, discoloration or other deterioration.

I claim: I

1. A motor fuel for a high compression, internal combustion, spark ignition engine which motor fuel consists essentially of a mixture of triptane and cyclopentane, each being present in the mixture to the extent of at least 25 volume percent.

2. A motor fuel for a high compression, internal combustion, spark ignition engine which motor fuel consists essentially of a mixture of triptane and cyclopentane, each being present in the. mixture to the extent of at least about 40 volume percent.

3. A motor fuel for a high compression. internal combustion, spark ignition engine which motor fuel consists essentially of triptane and cyclopentane wherein the triptanezcyclopentane ratio is approximately 6:4.

4. A motor fuel for a high compression, internal combustion, spark ignition engine which motor fuel consists essentially of volume percent triptane and 40 volume percent cyclopentane with approximately 4 cubic centimeters of lead tetraethyl fluid per gallon of triptanecyclopentane mixture.

ROBERT F. MARSCHNER.

REFERENCES CITED UNITED STATES PATENTS Name Date Stanly June 11, 1946 Number 

